+1.86%Safe swap — speedometer error is minor
Speedometer error
With a speedometer calibrated to 275/40R19, fitting 235/55R18 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 40.7 km/h | 25 mph | 25 mph |
| 60 km/h | 61.1 km/h | 37 mph | 38 mph |
| 80 km/h | 81.5 km/h | 50 mph | 51 mph |
| 100 km/h | 101.9 km/h | 62 mph | 63 mph |
| 120 km/h | 122.2 km/h | 75 mph | 76 mph |
Full comparison
275/40R19
Overall diameter702.6 mm · 27.66 in
Section width275 mm · 10.83 in
Sidewall height110.0 mm · 4.33 in
Circumference2207.3 mm · 86.9 in
Revolutions per mile729
Revolutions per km453
235/55R18
Overall diameter715.7 mm · 28.18 in
Section width235 mm · 9.25 in
Sidewall height129.3 mm · 5.09 in
Circumference2248.4 mm · 88.5 in
Revolutions per mile716
Revolutions per km445
+1.86%Safe swap — speedometer error is minor
Original
Overall diameter702.6 mm · 27.66 in
Sidewall height110 mm
Circumference2,207.3 mm
Revolutions / mile729.1
New
Overall diameter715.7 mm · 28.18 in
Sidewall height129.3 mm
Circumference2,248.4 mm
Revolutions / mile715.8
Speedometer & odometer error
The new tire changes overall diameter by +1.86%. With a speedometer calibrated to the original tire, that same percentage is how far the speedometer and odometer read off — a taller tire means your true speed is higher than indicated and the odometer under-counts distance.
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 40.7 km/h | 25 mph | 25 mph |
| 60 km/h | 61.1 km/h | 37 mph | 38 mph |
| 80 km/h | 81.5 km/h | 50 mph | 51 mph |
| 100 km/h | 101.9 km/h | 62 mph | 63 mph |
| 120 km/h | 122.2 km/h | 75 mph | 76 mph |
See individual specs: 275/40R19 · 235/55R18. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.